Difficult to answer without knowing all the pieces of the puzzle. The reason we have contracts and contract law is to provide a binding agreement between parties and to reduce that agreement to writing, so that there is good understanding of what has been promised. If the buyer has performed with respect to your contract, then it may be difficult to break it without some cost on your part. Of course, both parties have legal remedies as it pertains to that contract, and you may want to not only contact your agent, but an attorney, who can advise you as to your rights.
It may be important, Paul, if this is your homestead, and not an investment property. If you have had situations change and you no longer wish to sell your home, you'll likely be better off.
Call the experts to navigate your way through your recent decision.